Your system is currently using Microsoft's basic VGA driver which is limited to 640 x 480 resolution.
You need to download & install the model-specific Windows 7 graphics driver from your PC or laptop manufacturer's website, then you'll be able to increase the resolution & colour depth.
Or, if it's not a factory-built PC, download & install the graphics driver from the motherboard maker's website if it's an integrated graphics chip.
If it's an add-on PCI graphics card, download driver from that card maker's website.